[Mg-mmm] FW: Torque Values

[GRUNAU, ROBT]

 Morning MMMers,
I have been asked by the engine man for NA-0686 for some engine bolt torque
values. Below is my findings and answers.
Can anyone of you please add to the information or correct it if wrong.
Thanks for any information.
Bob Grunau in Canada where we are waiting for snow!!
PA-0531
NA-0686
KN-0389


My correspondence below:
35 will be OK for the head studs and nuts, these are special purpose built
rolled thread studs, the supplier says can go to 50 ft-lbs but that is way
too much for the head.

yes 35 may be on the high side for the 3/8" cheese bolts, Peter Green says
it is OK with oiled threads.  I tried the cheeses bolts on my PA block, same
design, and they pulled up OK at 35 ft-lbs. Took about 45 ft-lbs to break
them loose.

In general terms, BSF torque values are shown as about 5% less the NF torque
values for various size and similar grades of bolts.

I confirmed this this morning, using a new BSF Grade "R" bolts,  3/8"- BSF
Gr "R" at 35 ft-lbs torque to 45 ft-lbs torque turning the NUT, in
increments, no significant bolt elongation so I think 35 ft-lbs is OK.
Bolt/nut were stripped at 47.5 ft-lbs.

Repeated the test with new Grade "R" 3/8" BSF bolt by turning the BOLT, same
result, no stretch between 35 and 45 ft-lbs.
However in both cases, the bolt and nut were buggered going to 47.5 ft-lbs.

Doing a Google search for BSF recommended torques, , I found a page that
shows grade "R" 3/8" bolt recommended torque at 32 ft-lbs.  Same table shows
UNF at 34 ft-lbs recommended.
So I guess this confirms we are OK at 32 ft-lbs, max 35 ft-lbs for 3/8" BSF
bolt/nut.

Repeated the test with 5/16" BSF Grade "R" bolt and nut, here 20 ft-lbs and
below was OK
Soon as I went to 25 ft-lbs had significant bolt strech.
At 27 ft-lbs the bolt and nut were buggered.
The Google chart, 5/16" BSF-Grade "R"  fastener recommends 18 ft-lbs and
same chart says 19 ft-lbs for UNF.
So I guess 18 to 20 ft-lbs max is the range for 5/16" BSF grade 'R" new
bolts.

1`/4" BSF grade "R" torque is recommended at 9.1 ft-lbs, UNF = 9.3 ft-lbs in
the same table.

Hope this helps.
Bob

  35 seems high to me but I'll work up to it and see how it feels. I may
stop earlier if I think the bolts are stretching too much. Any other values
would be helpful.





  Head stud nuts are 35  ft-lbs, 40 absolute max.

  I assume bolts holding the cheeses are the same 35 ft-lbs and this was
confirmed this morning from Peter Green in the UK  who sold me the block and
crank.  So use 35 ft-lbs for the cheese bolts as these are also 3/8" BSF.



  He says remainder of bolts are not critical and so I would use NF bolt
torques.  Grade 5 ?????



  Peter also had some obvious observations, ie:

  1-Cheeses to be in and torqued before/during line boring the block.

  2-Cheeses to be marked and install same way around after line boring.

  3-Rear housing 9 bolts should be lock wired on final assembly.

  4-Rest of the engine is just common sense and he says should be no
problem.

  5-He agrees with usung the shell bearings, again he said cheeses to be
torqued before line boring shells.

  6-Chesses to be in and torqued for the cylinder boring.



  All common stuff and I know you know it.



  I will try to get more info re torques but not sure there is much more
available. I might try a few BSF bolts tightened to destruction to see what
torque they take before failure. Would this be usefull?  Also will go on the
internet and try to find BSF recommended torque values.



    Block's going in the machine but I need torque values for the various
fasteners. Can you assist?